the "LAStools.pdf" file in the LAStoolsCommon folder is not an Adobe Acrobat PDF but a small ASCI text file that adds new menu options to the Preference section of ERDAS IMAGINE 2014 (see its contents below). All the (rather limited) instructions are in the README.txt file ...
/*
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** PDF File -- Preference Definition File for LAStools.
*******************************************************************************
*/
title "LAStools";
lastools_enable("Enable LAStools") : "yes"
"Enable the use of LAStools in the ribbon and Spatial Modeler"
boolean "yes" "no"
hideon;
lastools_installation_path("LAStools Installation Path") : ""
"Full path to the LAStools installation";